1. Technical Field of the Invention
This invention relates to grinders, and more particularly, to an end mill grinder having two independently adjustable grinding wheels.
2. Description of Related Art
End mills are cutting tools commonly used in the manufacturing industry. An end mill typically has a plurality of helical cutting surfaces (flutes) having primary and secondary cutting surfaces, or clearances. Since the primary and secondary clearances directly contact a work piece during a cutting operation, the clearances eventually wear down. Thus, the primary and secondary clearances require periodic grinding or sharpening. Typically an end mill grinder utilizes a rotating cup wheel which is used to abrasively grind the clearances to sharpened edges. However, the typical process involves a two step procedure. First, the end mill is placed within an end mill grinder, adjusting the cup wheel to accommodate the sharpening of the primary clearance. An operator then sharpens the primary clearance of the end mill. In the next step, the cup wheel and end mill are positioned in a different manner for the sharpening of the secondary clearance. The operator then has to sharpen the secondary clearance of the end mill. A device is needed which provides an efficient and cost effective device for grinding the primary and secondary clearances of a tool having helical cutting surfaces.
Although there are no known prior art teachings of a solution to the aforementioned deficiency and shortcoming such as that disclosed herein, prior art references that discuss subject matter that bears some relation to matters discussed herein are U.S. Pat. No. 4,186,529 to Huffman (Huffman), U.S. Pat. No. 4,442,637 to Ahejew (Ahejew), U.S. Pat. No. 5,381,630 to Kinner (Kinner), and Patent Cooperation Treaty (PCT) Application Number WO 96/05940 to Laycock (Laycock).
Huffman discloses a method of grinding cutting edges and clearance surfaces on cutting tools such as end mills. A programmable servo-motor type control is utilized. All the grinding operations are completed at a single station in a series of consecutive grinding operations performed by the same grinding wheel and during which the tool remains in the same work holder. The various cutting edges and clearance surfaces to be ground are mathematically located and defined such that the grinding operations may be conducted under numerical control. However, Huffman does not teach or suggest two grinding wheels for simultaneously grinding a work piece. Huffman merely discloses a device which grinds a work piece with one grinding wheel in a series of operations. Thus, Huffman suffers from the disadvantages of requiring two or more steps to grind the work piece.
Ahejew discloses a simultaneously double-acting split abrasive grinding wheel for sharpening helix tools, such as end mill cutters. The wheel includes adjacent spaces and abrasive working strips of different proportions. The wheel is adapted in its use to a single pass, one-step operation which imparts primary relief angles, secondary clearances, and primary relief width spacing on the peripheral land surfaces of the tools being finished. However, Ahejew does not teach or suggest two independently adjustable grinding wheels for simultaneously grinding a cutting tool. Ahejew suffers from the disadvantage of utilizing a single grinding wheel which must be constructed for each type and size of cutting tool. A device is needed which can be utilized on a variety of end mills of different sizes.
Kinner discloses a resurfacing method and apparatus for brake disks or rotors utilizing dead centers to support the rotor, thus avoiding disk thickness variations which would result from support of the disk on roller bearings. Abrasive grinding wheels may then be used to effect the resurfacing of the disk, rotating in such a way relative to the disk rotation that a desired, surface pattern is produced on the disk. Kinner does not teach or suggest the independent movement of the grinding wheels. Additionally, Kinner is unable to grind primary and secondary grinding surfaces on an end mill. Kinner merely discloses a method and apparatus for grinding flat surfaces associated with brake rotors, but not helical cutting surfaces associated with end mills.
Laycock discloses a method and apparatus for dressing the grinding wheels of a dual head grinding machine. A dual wheel head grinding machine is disclosed having two heads. Each head carries a grinding wheel and a wheel dresser. The wheel heads are relatively movable to enable the first dresser to dress the second grinding wheel, or to enable the second dresser to dress the first grinding wheel. The two wheel heads are preferably movable in two coordinate direction. However, Laycock does not teach or suggest utilizing the two grinding wheels to simultaneously grind a work piece. Laycock merely discloses a device for dressing the grinding wheels.
Review of the foregoing references reveals no disclosure or suggestion of an apparatus or method as that described and claimed herein. Thus, it would be a distinct advantage to have an end mill grinder which utilizes independently adjustable grinding wheels to grind primary and secondary clearances on a cutting tool in a one step grinding operation. It is an object of the present invention to provide such an apparatus or method.
In one aspect, the present invention is an end mill grinder for grinding an end mill having a plurality of primary and secondary clearances. The end mill grinder includes a first grinding wheel for grinding the primary clearances of the end mill and a second grinding wheel for grinding the secondary clearances of the end mill. The second grinding wheel is located adjacent to the first grind wheel. Each grinding wheel includes a motor for rotating the grinding wheel. In addition, the end mill grinder includes a carriage located slightly below and adjacent the first and second grinding wheels, a finger guide attached to the carriage, and an end mill retainer for holding the end mill. The end mill retainer is attached to the carriage. The finger guide guides the end mill to move toward the first and second grinding wheels to simultaneously allow the first grinding wheel to grind the primary clearances and the second grind wheel to grind the secondary clearances of the end mill.
In another aspect, the present invention is an end mill grinder for grinding an end mill having a plurality of primary and secondary clearances. The end mill grinder includes a first grinding wheel for grinding the primary clearances of the end mill and a second grinding wheel for grinding the secondary clearances of the end mill. The second grinding wheel is located adjacent to the first grind wheel. The grinding wheels are rotationally driven by separate motors. In addition, the grinding wheels can be independently adjusted in position. A carriage is located slightly below and adjacent the first and second grinding wheels. The carriage has a finger guide and is rotatable to allow the end mill to be positioned on the finger guide prior to contacting the first and second grinding wheels. An end mill retainer is attached to the carriage for holding the end mill. The finger guide guides the end mill to simultaneously allow the first grinding wheel to grind the primary clearances and the second grinding wheel to grind the secondary clearances of the end mill.
In still another aspect, the present invention is a method of grinding a plurality of primary clearances and secondary clearances of an end mill in one grinding process. The method begins by adjusting a position of a first grinding wheel in relation to a second grinding wheel. The position allowing an outer edge of the first grinding wheel to grind the primary clearance of the end mill and an outer edge of the second grinding wheel to grind the secondary clearance of the end mill. Next, the end mill is affixed to a carriage having a finger guide. The first and second grinding wheels are then rotated. Next, the end mill is rotationally and horizontally translated to contact the rotating first and second grinding wheels. The first grinding wheel grinds the primary clearances and the second grinding wheel simultaneously grinds the secondary clearances of the end mill.